Refrigerating apparatus



Jan. 29, 1957 E. o. STOUT 2,779,529

REFRIGERATING APPARATUS Filed Sept. 3, 1952 IN VEN TOR. .El mer 0. Stout United States Patent REFRIGERATING APPARATUS Elmer 0. Stout, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application September 3, 1952, Serial No. 307,605

Claims. (Cl. 230-21) This invention relates to a refrigerating apparatus and more particularly to an adjustable capacity compressor for use in various types and sizes of refrigerating systems.

It has long been recognized that the capacity of a given compressor may be varied by varying the clearance between the end of the piston and the compressor head but the means for providing such an adjustment has long represented a problem due to the fact that the pistons reciprocate at high speeds and are subjected to varying pressures whereby conventional adjusting means are frequently jarred out of adjustment. It is an object of this invention to provide a simple and inexpensive means for adjusting the clearance which will not be jarred out of adjustment.

Still another object of this invention is to provide an adjustable plug for insertion into the end of a piston which will not tend to distort the walls of the piston when installed or adjusted.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Figure 1 is a fragmentary sectional view of a portion of a compressor showing my improved device set in a position to provide the compressor with a minimum cylinder clearance;

Figure 2 is a view similar to Figure 1 showing my device set in a position providing the compressor with increased cylinder clearance;

Figure 3 is a fragmentary view taken on the lines 3-3 of Figure 1 showing the top portion of parts of my adjustable cylinder clearance device; and

' Figure 4' is an enlarged fragmentary sectional View on an enlarged scale showing the relationship between the O-ring and the adjacent surfaces.

Referring now to the drawings wherein there is shown a preferred embodiment of the invention as applied to a conventional compressor of a refrigerating system, the compressor comprises a housing or casing provided with a bore 11 forming the cylinder of the compressor. A valve plate 12 is located on top of the housing 10 to substantially close the upper end of the cylinder or bore 11. A head 14 is located on top of the plate 12 and is held in place by suitable bolts 15 which extend through holes on the flange 14 and through holes provided in the plate 12. The ends of these bolts are threaded and extend into tapped holes provided on the flange 16 formed on the housing 10 in accordance with conventional practice. Gaskets may, if desired, be placed between the housing and plate 12 and between plate 12 and head 14 The head 14 is provided with a fluid inlet chamber 18 having an inlet port 19 adapted to be connected to the suction conduit or pipe of a refrigerating system (not shown). A web 21 on head 14 separates the inlet chamber 18 from the fluid outlet chamber 22 having discharge ports 23 adapted to be connected by a pipe to the condenser of the closed refrigerating system. The plate 12 ice 9 is providedwith inlet and outlet ports 26 and 27 respectively which are adapted to permit fluid to enter the cylinder 11 and also permit fluid to escape from the cylinder. These ports are normally closed by conventional inlet and outlet valves.

In the present disclosure there is a flat spring type inlet valve 28 which may be secured in any suitable manner between housing 10 and plate 12 within a recess 29 provided in the lower face of the valve plate 12 for normally closing the inlet port 26. A flat spring type discharge valve 31 is secured between plate 12 and head 14 within a recess 32 provided in the upper face of the valve plate 12. It is to be understood that while the valves 28 and 31 are herein shown more or less diagrammatically, they may be of any suitable construction.

I A piston 35 having suitable oil grooves therearound and located in the cylinder 11 is provided with a threaded counterbore or round cavity 36 in its upper closed end into which a disk-like plug or element 37 is threaded for a purpose to be hereinafter described. This plug or element 37 is of less thickness than the depth of the cavity 36 so as to permit the same to be threaded upwardly and downwardly within the cavity or longitudinally rela tive to the length of the piston 35.

The threaded plug or element 37 has been shown provided with a screw driver receiving groove 38 for use in rotating the plug relative to the piston whereas any other form of tool engaging means may be provided for use in adjusting the plug. For purposes of illustrating the invention I have shown a very simple type of piston whereas the invention is equally applicable to pistons having piston rings or other means for preventing leakage between the piston and the cylinder walls.

In small sized pistons the thickness of the piston wall adjacent the cavity 36 is thin enough so that it is not practical to use a set screw or other well known contrivances for locking the plug against rotation as the force which must be applied to the set screw or the like in order to be effective is suflicient to distort the piston walls. In the past it has been necessary to regrind the pistons after the plugs have been locked in place so as to compensate for the distortion which takes place when the set screws are tightened. Furthermore the set screws themselves tend to become loose after prolonged use.

I have discovered that the clearance adjusting plugs may be held in adjustment by means of an O-ring such as the O-ring 39 which is placed in a circumferentially extending groove 40 in the outer periphery of the plug 37. The O-ring is preferably made of polychloroprene or any other rubber like material which will not be affected by the refrigerant and lubricant.

By cutting a groove in the outer periphery of the plug which is wide and deep as measured from the peak of the threads on the plug and then using a 0- ring in the groove the plug will be held against rotation and will remain in adjustment for the life of the compressor. The above measurements have been given by way of illustration as the size of the groove and O-ring may be varied without departing from the spirit of the invention. If desired, the O-ring may be slightly larger than the groove as the extra material in the ring can flow into the corners of the groove. While the O-ring is preferably mounted on the movable plug it could be placed in a groove in the wall of the piston so as to contact the threads in the plug.

The piston 35 is provided with bearing openings which receive a wrist pin 41 to which is connected a connecting rod 42 in the usual and conventional manner. The lower end of the rod 42 is adapted to be connected to an eccentric portion of a shaft of the compressor for causing reciprocation of the rod 42 and consequently reciprocation Patented Jan. 29, 1957 of the piston 35 within the cylinder 12 as is well known and conventional in the art.

In compressors of the type herein illustrated the cylinder clearance is usually referred to as being the space within cylinder 11 intermediate the top of piston 35 and valve plate 12 when the piston is in the uppermost portion of the structure. By holding the cylinder clearance space to a minimum the compressor capacity is at or near its maximum and by increasing this space the compressor capacity is reduced. Thus, if the compressor is designed to have a rather great volumetric cylinder clearance and is driven by an electric motor of predetermined rating, the cylinder clearance of the compressor may be reduced to increase the capacity and efiiciency of the compressor, within predetermined limits without overloading and damaging the electric motor. By virtue of this expedient it is possible to render the same or similar compressors capable of being used in widely diiierent refrigerating systems. Gonsequently, the necessity of manufacturing a large number of compressor sizes for refrigerating systems of different capacities at least within a predetermined capacity range has been eliminated.

The simplicity of the adjustable cylinder clearance setting device is such that the device may be changed by a Serviceman after installation of the refrigerating system to compensate for various factors in the particular system involved. The serviceman needs only to remove the compressor head 14- and valve plate 12 together with the valves 28 and 31 to gain access to the upper end of the piston 35 and may then simply rotate the plug 37 relative to the piston to thereby increase or decrease the cylinder clearance within the compressor as desired. This may ail be done without exerting any pressures which might distort the piston.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. In combination, a compressor having a piston and cylinder, an element carried by said piston and having a substantial surface area exposed to the interior of said cylinder, said element being adjustable longitudinally relative to the length of said piston to increase or decrease the cylinder clearance within said compressor, said element having a circumferentially extending groove in its outer periphery, and an C-ring disposed within said groove for frictionally engaging a portion of the piston so as to restrain movement of said element relative to said piston.

2. A piston of the character described comprising a thin Walled tubular portion forming an axially extending chamber, a filler plug within said chamber and having a screw threaded connection to said tubular portion, a groove intermediate the ends of said screw threaded connection, and an O-ring within said groove for engaging the wall of said chamber for restricting relative rotation between said filler plug and said tubular portion.

3. in combination, a cylinder element, a piston within said cylinder element, a cylinder head, said piston having a threaded recess formed in its one end adjacent said cylinder head, an adjustable plug disposed within said recess and having threads engaging the threads in said recess, a circumferentially extending groove provided in the outer periphery of said plug, and an Caring within said recess for frictionally engaging said piston and said piiw so as to restrict relative rotation between the piston and the plug.

4. in combination, a cylinder element, a piston within said cylinder element, a cylinder head, said piston having a threaded recess formed in its one end adjacent said cylinder head, an adjustable plug disposed within said recess and having threads engaging the threads in said recess, a circumferentially extending groove provided in the outer periphery of said plug, and an O-ring within said recess for frictionally engaging said piston and said plug, said circumferential l-y extending groove being substantially square in cross seetion whereby a portion of the material of said O-ring is free to lac-compressed into the corners of said groove.

5. In combination, a piston elemept having a recess formed in its outer end, a clearance adjusting plug element within said recess, the inner wall of said recess and the outer periphery of said plug element having comples men ary threads formed thereon whereby the plug element may be adjusted longitudinally within said recess, one of said elements having a groove formed thereon directly opposite the other of said elements, and an 0- ring disposed within said groove for frictionally engaging both of said elements for restricting relative rotation of said elements.

efer nces Cited n t e ti e o this p te NI ED STA E PA E S 665,448 Lapham .a J an. 9, 1901 996,937 Mulock July 4, 1911 2,396,005 Gross Mar. 5, 1946 2,429,426 Phillips Oct. '21, 1 947 2,437,843 Van Ness Mar. 16, 1 948 2,647,683 Schweller Aug. 4, 1953 O E GN PATE 135,126 Great Britain Nov. 20, 1919 646,343 France ..'Nov. 9, 1928 THE RE ERENC S A Handbook on Synthetic Rubber Packings, pub- 'lished by E. F. 'Houghton Co. (Chicago), first ed., 1947 (Fig. 21 on page 53 relied on). 

